Roll seal for vacuum strip-treating chamber



Feb. 6, 1968 W. s. ALLEN ROLL SEAL FOR VACUUM STRIP-TREATING CHAMBER 2 Sheets-Snee l Filed July 16, 1965 IMI/ENTOR W/LL/AM 5*. ALLE/V 5J Altar/ley Feb. 6, 1968 w. s. ALLEN 3,367,667

ROLL SEAL FOR VACUUM STRIP-TREATING CHAMBER Filed July 16, 1965 2 Sheets-smeet u i /l l l l J/ /3\` /le il l \7 27 7\ \//5 20 l5-f 28 28 v 26 l 26 s s 22 22M a U 23" 23- o O 23 23 25l 24 o @$5 l5 /9 0 24 o b* o 25g v 23- 23 25 o /7 m) o 23 t L// a r/ I z v Tia-.4

I'NVE/VTO? WILL/AM '5. ALLEN Ney @M60/M United States Patent 3,367,667 ROLL SEAL FOR VACUUM STRIP-TREATING CHAMBER William S. Allen, Pittsburgh, Pa., assigner to United States Steel Corporation, a corporation of Delaware Filed July 16, 1965, Ser. No. 472,516 4 Claims. (Cl. 277-237) ABSTRACT F THE DISCLOSURE A unit of a multiple-box seal for the entry of traveling strip into a vacuum chamber contains a cluster of three rolls journaled in the box, in parallel arrangement, two alongside one another and the third in the valley between the other two. Adjustable toggle linkages are provided for raising the middle roll against spring pressure so that slight clearance is provided for strip threaded between the rolls. Sealing blades engage the faces of the rolls and sealing shrouds the end-s of the rolls.

This invention relates to roll seals, and in particular, to seals of this type for limiting leakage into a vacuum processing chamber around strip traveling therethrough Certain industrial processes such as coating by metalvapor deposition, must be conducted in a high-vacuum chamber. For continuous, high-speed operation this necessitates seals at the entrance to and exit from the chamber, through which the strip passes before and after treatment. Conventional roll seals, i.e. pinch roll-s tightly engaging the strip, are one form of such seal but, if the rolls are of metal, marring of the strip results. Rolls of a rubber-like material would avoid this difficulty but the temperatures of operation are too high for rubber to withstand. n

I have invented a roll seal for a vacuum strip-treating chamber which overcomes the aforementioned disadvantage and limitation. I employ as a seal, a group or cluster of three chromium-plated rolls, one fitting in the depression between the other two, and lead the strip around the rolls successively in a sinuous path while maintaining a spacing between adjacent rolls slightly greater than the thickness of the strip. Il also provide seals for the peripheries and ends of the rolls. Thus the only space left through which leakage may occur is the clearance between the strip and rolls and such leakage as occurs may readily be removed by pumping. By utilizing several seals in series and pumping their enclosing chambers separ-ately, it is possible to produce -staged pres-sure reduction and a iinal vacuum of a very low order, such as 0.05 mm. of mercury.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the present preferred embodiment. In the drawings:

FIGURE l is a side elevation showing a series of seals according to my invention;

FlGURE 2 is a longitudinal vertical section through -a single roll-seat unit showing parts in elevation;

FIGURES 3 and 4 are full and partial cross sections, respectively, taken on the planes of lines lll-IH and lV-lV of FIGURE 2.

Referring now in detail to the drawings and, for the present, particularly to FIGURE 1, a complete seal for either the entrance or exit end of a vacuum strip-treating chamber comprises a plurality of roll-seal boxes 10, with spacer or separator boxes 11 therebetween. A series of alternating-boxes and 11 tightly sealed together will be arranged in line with both the entrance to and the exit from the vacuum strip-treating chamber. Each box is of ice plate construction, has one side removable to permit access to the interior, but tightly sealed, and openings 12 for the passage of strip in opposite ends. The several boxes constituting a complete seal, of course, are tightly connected together in any convenient manner and the joints therebetween are sealed vacuum tight. Each box has an exhaust outlet 10a or 11a connected to a suitable vacuum pump (not shown).

FIGURES 2-4 illustrate one of the roll-seal boxes in greater detail and the construction of the rol-l group or cluster disposed therein. Referring more particularly to FIGURES 2 and 3, a housing 13 is disposed in each box 10 between spaced positioning rails 14 secured to the bottom of the box. The housing consists of spaced parallel side plates 15 connected by cross bars 16. A pair of spaced parallel rolls 17 and 18 have their shafts journaled in bearings 19 secured to plates 15 and extend substantially the full distance therebetween as shown in FIGURE 3. Between rolls 17 and 13 a third roll 20 has its shaft journaled in vbearings 21 movable vertically in ways 22 secured to plates 1-5, which have slots to permit vertical adjustment of the roll shaft. Rolls 17, 18 and 2d are chromium plated and polished.

Means are provided for adjusting roll 20 vertically in the form of toggle linkages 23, each including a nut 24 threaded on a screw shaft 25. This shaft has portions near its two ends threaded in opposite directions so that on rotation thereof in one direction, the nuts will be drawn together raising bearings 21 while rotation in the other direction will move the nuts apart, lowering the bearings. The linkages are pivotally connected to ears 23a depending from bearings 21 and t0 ears 2311 projecting from plates 15. Compression springs 26 having adjustable back-up screws 27 engage hearings 21 and urge them downwardly to the limit permitted by the adjustment of nuts 2d. Screws 27 are threaded through lugs 28 projecting from plates 15. Shaft 25 may be operated by a crank 25a journaled in a vacuum-tight bearing in a wall of box lil and connected to the shaft by a flexible joint 25h.

Entry and exit chutes 29 and 30 having a width equal to the length of the face of rolls 17, 1S and 20 are mounted Ibetween plates 15 and extend from the roll faces to flexible diaphrams 30a secured to the end walls of box 10, overlying openings 12 therein. Sealing shrouds 3l recessed into the inner faces of plates 15 engage the sides of chutes 29 and 3l] and the ends of rolls I17, 18 and 20. Each shroud is made up of a graphite plate or a layer of Teflon resin sheet 32 and is backed up by a leaf spring 33. Chutes 29 and 30 are provided with recesses 29a for holding spring-urged sealing blades 37 of graphite. The blades engage the faces of rolls 17, 18 and 29. The diaphrams permit contraction and expansion of chutes 29 and 3l) to allow for temperature changes.

In operating a roll seal according to the invention, rolls 20 are rst raised from the illustrated position by rotation of shaft 25, to facilitate threading the strip therebetween as indicated at S in FlGURE 1. The rolls 20 are then lowered to positions in which they almost but not quite, pinch the strip against rolls 17 and 18. ln other words, a slight clearance, say .002, in excess of the `strip thickness is left between the rolls so they will not mar the product. This clearance, of course, permits a slight leakage of air but such minor leakage as occurs may readily be handled by the vacuum pumps. All other spaces where leakage might occur are tight-ly sealed off. The rolls 17, 18 and 2t? are driven by the frictional engagement thereof with `the advancing strip but the frictional drag imposed by the rolls is not suicient to cause slippage and marring of the strip.

My invention has several important advantages. It affords close sealing of the space around the strip without actual Contact therewith. The closeness of the seal is readily adjustable for dilierent strip thicknesses. The resilient back up for the shrouds sealing the spaces at the ends of the rolls allows for thermal expansion and ce-ntraction thereof without jamming or loss of sealing. 1n addition, the springs backing up the movable roll bearings permit opening up of the roll gaps for passage of a strip portion of a thickness greater than normal. Adjust-ment of the movable sealing rolls may easily be made during operation, as needed to compensate for thermal expansion, as in starting up.

Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as well any change 0r modification therein which may be made without departing from the spirit and scope of the invention as Iset forth in the claims.

I claim:

1. Apparatus for sealing the entrance and exit of a vacuum strip-treating chamber comprising a box having entry and exit slots in the ends thereof, a roll housing in said box, a pair of parallel rolls journaled in said housing, ya third parallel roll riding in the valley between said pair of rolls to provide two nips so that strip passing through the box follows a sinuous path and goes through both nips, sealing means carried by said box above and below said slots and engaging said rolls, and means mounting said third roll for movement toward and from said pair of rolls, said mounting means including spaced bearings slidab'ly mounted on said housing and in Awhich said third roll is journaled, springs engaging said bearings and constantly urging them toward said pair of rolls, a toggle linkage pivotally connected to each bearing therebelow and to a fixed point on said housing, each linkage including a nut pivoted intermediate the links thereof, and a common shaft threaded through the nuts of both linkages whereby rotation of the shaft in one direction extends both linkages to move said bearings away from said pair of rolls against the force of said springs.

2. Apparatus as dened in claim 1 characterized by said shaft being accessible on the exterior of said box for effecting movement of said bearings.

3. Apparatus as defined in claim 1 in which said sealing means are in the form of chutes carried by said box extending inwardly from said slots, and sealing blades on said chutes engaging the rolls.

il. Apparatus as dened in claim 1, characterized by sealing shrouds between the ends of said rolls and the sides of said housing.

References Cited UNITED STATES PATENTS 1,208,339 12/1916` Lewis 68-263 1,633,121 6/1927 `Minton` 2,434,003 1/1948 Morrison 34-242 X 2,707,162 4/1955 Fries 118-49 X 2,844,889 7/1958 Corbett 34-242 3,032,890 5/1962 Brick et al. 34-242 X 3,260,000 7/1966` Schiffer 34-242 CHARLES A. /VLM'UTH, Primary Examinez'.

I. P. MCINTOSH, Assistant Examiner. 

